1. Field of the Invention
The present invention relates to a cutting insert.
2. Description of the Related Art
Generally, a cutting insert is coupled to a cutting tool mounted on a machine tool, to be used in cutting a workpiece to be cut which consists of iron, nonferrous metals, non-metal materials, etc.
U.S. Pat. No. 5,052,863 discloses an example of the cutting insert, which discloses a cutting insert (hereinbelow, ‘conventional cutting insert’) as the one illustrated in FIG. 1. For reference, FIG. 1 corresponds to FIG. 6 provided by U.S. Pat. No. 5,052,863, without any modifications to the reference numerals for convenience of explanation.
To be specific, the conventional cutting insert is used as a peripheral rotary milling cutter which includes a cylindrical holder and a plurality of replaceable cutting inserts arranged along circumferential direction, in which at least one cutting edge is provided between rake surface and relief surface of the insert.
Further, the conventional cutting insert is so configured that narrow flank surface portion 24a is gradually decreased in size in a direction from the raised cutting corner edge portion to lowered cutting corner edge portion, and the relief angle is substantially not varied along a lengthwise direction of the cutting edge.
Meanwhile, high speed and high feed cutting is subject to great possibility of having excessive cutting loads on specific portion of the cutting edges depending on processing conditions, and if this happens, the cutting edges of the specific portion of the conventional cutting insert can possibly be broken. Accordingly, it is necessary to provide a cutting insert, which has increased cutting performance, and also has increased rigidity on specific portion which can be subject to excessive machining load.